# Conversion Factor

How can I find my conversion factor in kWh? There’s a line on my statement which mentions Volume conversion factor but it’s value is 2.83, and I seem to have a figure from a previous energy supplier of 32.5 - which seems a dramatic difference. Is 2.83 my actual figure, or do I have to do some calculation to find out the true value? Thank you.

This may help:

The ‘Volume Conversion Factor’ is zero for a metric (cu metre) meter, and 2·83 for an imperial (cu ft) meter.
The figure from your previous supplier is the approximate number of kWh delivered by one unit (100 cu ft) recorded by an imperial meter.

Hi, thanks for that - my meter is cubic feet, so does that mean my conversion factor is 2.83 then? Or is that the volume conversion factor and just a conversion factor is something different? Thank you.

Hi, thanks for that - my meter is cubic feet, so does that mean my conversion factor is 2.83 then? Or is that the volume conversion factor and just a conversion factor is something different? Thank you.

Your meter is measuring in hundreds of cubic feet. The volume conversion factor of 2.83 converts hundreds of cubic feet into cubic metres. You then continue from there using the metric formula for cubic metres to kWh as detailed on your statement.

Ok, I’ll try phrasing this in a different way. I understand where to find the various figures used to calculate conversion factor as outlined above. However, I don’t want to do a conversion myself. I have an app to track meter reads and costs. It asks me to enter a value for “Conversion Factor”. Which of all the figures mentioned above is the one that I enter? Thank you.

If, a you say, your meter reads in cu ft, then it’s 2·83.

Ok, I’ll try phrasing this in a different way. I understand where to find the various figures used to calculate conversion factor as outlined above. However, I don’t want to do a conversion myself. I have an app to track meter reads and costs. It asks me to enter a value for “Conversion Factor”. Which of all the figures mentioned above is the one that I enter? Thank you.

Ah! Now I understand. It’s always best to ask the question you actually want to answer, rather than what you think is the question related to the problem. There are four parameters used to convert gas volume into kWh, and as you know these are all detailed on your statement. Since your app allows you to enter only one parameter for the conversion you need to combine all four parameters into one overall “conversion factor” as called by your app.

From my latest bill,

Volume conversion factor: 1.00 for a metric meter, or 2.83 for an older imperial meter. Volume correction: 1.02264 Calorific value: 39.3 Convert to kWh: 3.6

The equation is,

meter units * volume conversion factor * volume correction * calorific value / convert to kWh = kWh

Simplify to one parameter,

Overall conversion factor = volume conversion factor * volume correction * calorific value / convert to kWh

And so,

Metric overall conversion factor = 1 * 1.02264 * 39.3 / 3.6 = 11.16382 Imperial overall conversion factor = 2.83 * 1.02264 * 39.3 / 3.6 = 31.5936

Since you have an imperial meter you need the second of those two values. Note that this is close to the value given by your previous supplier but not exactly the same. The calorific value varies with the quality of the gas being supplied, and so you either need to update this each time you receive a statement or accept that you are only calculating approximate values that wont match exactly with the billed usage.

Oh, don’t forget the calorific value changes on a daily basis due to temperature, pressure, source of the gas etc etc - https://www.nationalgridgas.com/data-and-operations/calorific-value-cv and is variable also depending on your region.

Oh, don't forget the calorific value changes on a daily basis due to temperature, pressure, source of the gas etc etc - https://www.nationalgridgas.com/data-and-operations/calorific-value-cv and is variable also depending on your region.

I said that

Is the value on the monthly bill an average then, if it changes daily? I presume it must be.

I was a little annoyed when I first moved to Bulb, since their calorific value was 5% higher than my last bill from Scottish Power, meaning it was a 5% increase in cost that I hadn’t accounted for when making comparisons.

Yes they take the average CV value over the month, there is a website you can check the CV for your area, it gives the daily figures.